/Engine/Source/Editor/UnrealEd/Public/EditorModeRegistry.h
Registers an editor mode. Typically called from a module's StartupModule() routine.
void RegisterMode ( FEditorModeID ModeID, [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [IEditorModeFactory](API\Editor\UnrealEd\IEditorModeFactory) > Factory )